In the mass production of snack foods or other food products, the extrusion process may be employed because it economically provides a high volume of product having a uniform configuration and structure. Usually, when designing an extrusion process and/or apparatus, the desired properties of the end product must be considered along with the processing characteristics of the individual components that make up the product. Often, these considerations may require the use of a specific method and/or apparatus to achieve a particular result.
In the design of mass production facilities for the coextrusion of snack products, flow properties such as viscosity, handling properties or other processing characteristics of a particular material stream must be factored in. Certain material streams may be sensitive to variations in flow rate or direction caused by a circuitous flow path or obstacles in the flow path. Problems may arise such as high back pressure, insufficient mass flow rate and non-uniformity of individual layers in the product.
Certain materials may require an extremely smooth and uninterrupted flow path in order to remain either in an integral flow stream or a divided flow stream which is easily reformed into an integral one. If a change of direction occurs or an obstacle is present in the flow path, reformation may be difficult to achieve because the discrete streams may not reunite to form a uniform, integral flow. In this instance, the resultant product may have unacceptable qualities such as seam lines or striations.
In other instances, smooth flow paths for the individual streams may be required to prevent back pressure in pumps and related equipment and low mass flow rates, especially for viscous materials.
Also, coextrusion apparatus often have many potential leak points, due to their multiple parts, complex configurations and high operating pressures. As the number of concentric layers increase in a coextrudate, for example when three or more layers are desired, die complexity increases quite rapidly. Generally, more parts are needed, flow paths become disrupted by inlet passages, more potential leak points are created, tolerances in the concentric passageways become tighter, flow path directions change more frequently or abruptly, and back pressures increase. These problems tend to become even more exacerbated as the desired final diameter of the coextrudate rope and final product decreases. In producing coextrudate ropes wherein one or more concentric layers expand upon exiting the extrusion die, the concentric passageways must be even smaller in diameter to achieve a desired final coextrudate rope diameter. For example, when coextruding a plurality of fillers with an expandable farinaceous-based cooked casing, from a cooker extruder, the casing may expand substantially upon exiting the triple coextrusion die. The outer concentric passage for the casing, and hence the remaining inner passageways for the fillings must be sized substantially smaller than the desired diameter of the expanded final product.
After the extrusion step, certain food or snack products are sometimes shaped in a manner to make them more aesthetically pleasing and/or bite-size. This usually requires post-extrusion processing by way of, for example, a candy making machine which severs the rope into individual pieces having the shape of the individual molds of the candy machine. In the instances where this type of post-extrusion processing is used, the extrudate rope to be fed into the post-extrusion step should have a diameter substantially the same size as the diameter of the final product or the mold. Matching of the diameters helps to avoid the production of excessive scrap during the continuous molding operation. For example, if a peanut shell-shaped expanded snack product is desired, the expanded extrudate rope should be substantially the same in diameter as the diameter of the final peanut product. The final product diameter may be relatively small if simulation of an actual peanut shell size or bite-size pieces are desired.
U.S. Pat. Nos. 4,715,803 and 4,748,031 to Koppa disclose an extruder which provides a triple coextruded product having an inner layer, which is surrounded, or enrobed, by an intermediate layer, which is surrounded, or enrobed, by a third outer-most layer. The inner layer is a dough having a chewy and moist texture when baked and the outer layer is a dough having a crispy texture after baking. These patents relate specifically to the introduction of a barrier material between the two dough layers in order to achieve the desired product stability and shelf life. The moisture barrier is injected through the outer cylindrical layer in a tube upstream of the extruder outlet.
A pillow-shaped product, having an outer layer of expanded dough and two different filler materials is disclosed in U.S. Pat. Nos. 4,698,004 and 4,888,192 to Ramnarine. The penetration of the outer expansible dough by the inner fillers in the end product is avoided through the use of a nozzle which can be adjusted to compensate for the effects of the fluid flow of the individual streams. The process is directed to the side-by-side extrusion of the filler materials.
U.S. Pat. No. 3,241,503 to Schafer discloses a die for the manufacture of cookies with concentric rings of different colored dough. The process involves introducing successive layers of dough through conduits perpendicular to the die into annular cavities surrounding a longitudinally extending bore.
U.S. Pat. No. 4,834,999 to Matthews et al discloses triple coextruding a meat-based product comprising whole muscle body surrounding a core stuffing, an outer casing, and an annular layer of fat between the whole-muscle body and the outer casing.
U.S. Pat. No. 5,686,128 to Tracey et al discloses the production of a triple coextruded snack having a casing material which may be a dough or an expansible dough such as a cookie dough, or cracker dough enrobing two fillers. The triple coextrusion apparatus includes a unitary die block for all three materials and has smooth and uninterrupted flow paths. A small diameter extrudate rope is produced with a central filler enrobed by an outer filler, subsequently enrobed by an outer casing formed from multiple streams. The outer casing material streams reform into an integral concentric layer having no or substantially no seam lines or striations in the outer casing. The extrudate ropes may be sufficiently small in diameter, even when the casing is expanded, to allow feeding into a candy machine for shaping by molding or crimping to produce small diameter snack products without substantial waste or scrap material.
Japanese Patent Publication No. 60-070036, published Apr. 20, 1985, discloses production of three-layered soft food by extruding a core layer, interlayer, and outer layer at the same time to mold a three-layered cylindrical material, rolling the material while cut into a given size using a cutting and rolling means, and molding the material.
Coextrusion is also used to manufacture multi-layered plastic articles. For example, U.S. Pat. No. 4,185,954 to Murakami, et al., U.S. Pat. No. 5,318,417 to Kopp, et al., and U.S. Pat. No. 5,324,187 to Cook describe apparatus and processes for manufacturing multilayered tubular or hollow plastic products where each outer layer is successively added downstream to surround the upstream added inner material or materials.
U.S. Pat. No. 4,125,585 to Rosenbaum, U.S. Pat. No. 4,731,002 to Spence, et al., and U.S. Pat. No. 4,846,648 to Spence, et al. describe method and apparatus for manufacturing multilayered plastic pipe where the inner layer is injected across the central layer and through a spider.
U.S. Pat. No. 4,364,882 to Doucet describes method and apparatus for manufacturing multilayered plastic pipe where the central layer is injected across the outer layer through a trefoil.
German patent DT 3044535 (published Jun. 24, 1982) describes method and apparatus for manufacturing multilayered plastic pipe where one or two central layers are injected across the outer layer.
In producing an extruded baked good having a desired bar shape, such as a FIG NEWTON®, configuring die orifices to the same bar shape or cross-section desired for the baked good can result in an extruded, unbaked dough with the desired shape. However, the dough rope shape or cross-section may change substantially during baking due to oven spread resulting in an undesirable baked good shape, such as a baked product which is too thin. The shape of the die orifices may be changed, for example to increase the height of the extruded dough rope so that upon baking the extrudate rope spreads into the thinner desired shape. However, it has been found that the use of concentric, circular die orifices to produce a cylindrical dough rope results in insufficient oven spread to produce a desirable, bar-shaped baked good.
It has also been found that in producing a baked, bar-shaped product having a plurality of concentric fillings, which are visually apparent at each end of the bar, the use of a roller to flatten a cylindrical dough rope to achieve a desired bar shape results in sticking of the outer dough casing to the roller and tearing of the dough rope and base cake. Also, it has been found that in producing a triple coextruded dough rope having a cross-section with a substantially smaller height than width, without the use of a roller, the middle layer or filling tends to flow towards the ends rather than the top and bottom. The resulting baked product tends to have a substantially uneven middle concentric layer which is excessively thin or discontinuous at the top and bottom, particularly as the cross-sectional height to width ratio of the dough rope decreases.
Also, as the height or thickness of the dough rope decreases along with the thickness of the filler layers, cutting of the baked rope tends to result in more visual smearing of one layer of filling into another.
The present invention provides a method for producing a triple coextruded baked good having a bar shape with a substantially smaller height than width, such as a FIG NEWTON® shaped product, without the need for post-extrusion shaping or mechanical flattening of the dough with a roller, thereby avoiding sticking and tearing of the dough by the shaping equipment. Triple coextruded bar shaped products such as cookies with dissimilar fillings, such as a fruit filling and a cheese-cake filling, may be continuously produced on a mass production basis. The present invention provides for the production of baked goods having distinct, at least substantially uniform concentric fillings which are visually apparent at opposing cut ends of the baked piece. Undesirable excessive flow of a middle filling or layer towards the cross-sectional ends or sides rather than the top and bottom of the coextrudate is substantially reduced. Control of the flow of the middle filling results in a baked product having a substantially even middle concentric layer which is desirably uniformly thick and continuous at least across the top and bottom. Cutting of the baked product is accomplished without any substantial visual smearing of one layer of filling into another.